What's my next move - #3 plug STILL BLACK !!

[hikermikem]

OK, last update...

Got home last night & the bike ran lousy all the way home. Feels like
a dropped cylinder; vibration, stumbles, sounded "ticky"...

Can't imagine what could have happened between the morning ride & the afternoon ride ? It just sat in the parking lot, looking pretty...

Once home, played with the mix screws a bit to optimize the idle - then went for ride. Still stumbly & the forever black #3 plug.

Getting to the end of the riding season here for me in NE (low 40's this morning) - I'm starting to think more & more about my real true love: skiing fresh powder in VT !!!

Besides, my 1100 is REALLY feeling lonely & neglected, I have to spend some time with her before she gets too mad...

Anyone want to buy a GS850GLZ ??

Frustrated,

mike

[49er]

Got home last night & the bike ran lousy all the way home. Feels like
a dropped cylinder; vibration, stumbles, sounded "ticky"...

Can't imagine what could have happened between the morning ride & the afternoon ride ? It just sat in the parking lot, looking pretty...

Once home, played with the mix screws a bit to optimize the idle - then went for ride. Still stumbly & the forever black #3 plug.

Getting to the end of the riding season here for me in NE (low 40's this morning) - I'm starting to think more & more about my real true love: skiing fresh powder in VT !!!

Besides, my 1100 is REALLY feeling lonely & neglected, I have to spend some time with her before she gets too mad...

Anyone want to buy a GS850GLZ ??

Frustrated,

mike

Mike, you've eliminated spark by a fairly thorough analysis, which really only leaves excess fuel or serious oil fouling of the plug. If it's an oil issue, you should be noticing the engine smoking on decel or even when reved into the upper rev range, with a need to top up your oil level on a monthly basis. If these symtoms aren't present, it leaves fuel delivery to that cylinder. IMO, you need to recheck the following areas.

1. Check that there is no partial restriction to the #3 carb inlet in the airbox.
2. You have eliminated a faulty needle valve/wrong float level by confirming the 5mm of fuel in each bowl.
3. You said that the problem is most obvious in the mid range of the rpm which probably equates to 1/2 to 3/4 throttle positions. This points to a problem with the needle jet or the jet needle on #3 carb. If a PO has swapped out these, you could have the wrong combination on that cylinder. It's about the only logical conclusion, going on the acccuracy of the information supplied!!

[hikermikem]

Thanks 49'er, I appreciate your thinkin' this through.

I have ordered one new jet needle & seat to replace the set in carb #3. I have to remove the carb rack from the bike to install 'em, so I'm inclined to just dip all 4 carb bodies as long as I have it off. I don't really want to, but I suppose it would be in my best interest to do so...

I may as well double check the valve clearances too, there was some carbon in the cylinders (based on looking in the plug holes) when i got this baby. I put a capfull of seafoam in the oil when I changed it out & ran about 150 miles that way - changed out that oil & filter and put fresh 10-40 dino in... The oil was very black & the bottom of the drain pan had quite a bit of organic particulate matter in it - carbon crud I assumed, no metal bits. I was wondering if the valves were really seated when i adjusted them the first time, but a compression test shows good compression.

Anyway, can't hurt to check them again, maybe a valve or 2 isn't opening??

Lots of rework staring at me at a time when the season is winding down, so maybe this will turn into a "next" year project.

Thanks,

mike

[KEITH KRAUSE]

Just wondering what the history is of the parts and the bike.
Did it run fine at one time and then start to have this trouble or did you inherit this problem?
Replacement carbs can be a lot of trouble due to neglect and/or poor servicing.
You still haven't tested it at specific throttle positions, chopped off, and read the plug to see any changes. It sounds like the jet needle circuit to me. If you swapped jet needles and saw no change, that suggests the needle jet could be worn.
It could also be a clogged primary air jet as I mentioned. You didn't say you proved it was OK/clear.
I'm also wondering how good the carb synch is. Have you proven vacuum is similar to the other 3? Have you also tried another plug?

[hikermikem]

Just wondering what the history is of the parts and the bike.
Did it run fine at one time and then start to have this trouble or did you inherit this problem?

Don't know any of the past history - bike was sitting (covered) for 15 years when I bought it. The guy I bought it from never ran it, just stored it for the last 3 of of the 15 years. Approx 7K on the ticker.

Replacement carbs can be a lot of trouble due to neglect and/or poor servicing.

Bike sat with gas in the tank/carbs for all that time - VERY YUCKY when I started cleaning the fuel system up. All stock parts, obvious I'm the first guy in there...

I've dipped/rebuilt 3 sets of CV carbs prior to this one, but still I know I may have not done a good enough job - each body sat 24 in my "old" can of Berryman's, then another 24 hrs in a "new" can of Berryman's. Tank's been POR'ed & a new petcock as well...

You still haven't tested it at specific throttle positions, chopped off, and read the plug to see any changes. It sounds like the jet needle circuit to me. If you swapped jet needles and saw no change, that suggests the needle jet could be worn.

True, I've not done that yet - I am planning to do so. I ordered one new jet needle & needle jet to replace the ones in#3, just as a last resort before tearing it all apart again.

It could also be a clogged primary air jet as I mentioned. You didn't say you proved it was OK/clear.

When I had it apart the other day I verified that passage was clear.

I'm also wondering how good the carb synch is. Have you proven vacuum is similar to the other 3?

I synced them using a Morgan Carbtune, 1 & 4 are equal, 2 & 3 are a little less. Haven't re-synced since I changed the mix screws settings, or swapped around the jet needle, but didn't "ungang" them or touch the sync adjustment screws...

Have you also tried another plug?

Yes. swapped between 3 & 4, and also used a brand new one - same result.

[hikermikem]

Happy update !!!

While the forum was down, I FINALLY fixed my carb problem that resulted in a fouled #3 plug, and made the engine run on 3 cylinders.

The problem turned out to be a badly worn needle-jet. I bought 4 new OEM ones and the all my problems vanished. In fact... this bike now runs excellent!!

I cut the "bad" needle-jet in half length-wise to inspect it: the corrosion on the inside diameter resulted in lots of voids that allowed fuel to bypass the jet needle and reach the outlet holes where it shouldn't have gotten to, thus dumping fuel into the carb and fouling the plug.

Although I inspected these needle-jets when I initially took the carbs apart, I guess I didn't really look inside them too hard. I may just start routinely replacing them on subsequent carb rebuilds.

I just re-sync'ed the carbs this evening and this bike is running very, very nicely!!! It's a shame the riding season is coming to an end here in NE, although it's been unseasonably warm lately .

Thanks for hanging around to hear me out.

[49er]

While the forum was down, I FINALLY fixed my carb problem that resulted in a fouled #3 plug, and made the engine run on 3 cylinders.

The problem turned out to be a badly worn needle-jet. I bought 4 new OEM ones and the all my problems vanished. In fact... this bike now runs excellent!!

I cut the "bad" needle-jet in half length-wise to inspect it: the corrosion on the inside diameter resulted in lots of voids that allowed fuel to bypass the jet needle and reach the outlet holes where it shouldn't have gotten to, thus dumping fuel into the carb and fouling the plug.

Although I inspected these needle-jets when I initially took the carbs apart, I guess I didn't really look inside them too hard. I may just start routinely replacing them on subsequent carb rebuilds.

I just re-sync'ed the carbs this evening and this bike is running very, very nicely!!! It's a shame the riding season is coming to an end here in NE, although it's been unseasonably warm lately .

Thanks for hanging around to hear me out.

Thanks for feeding back your results. Many don't have the manners to manage that part. Enjoy your riding, whats left of it.
Cheers.

[tfb]

Another excellent result!

Be sure to follow-up with a carb-synchronisation now that the dust has settled. I used to think that they were kind of optional until a plug-fouling problem was cured by a carb-sync...

[hikermikem]

Another excellent result!

Be sure to follow-up with a carb-synchronisation now that the dust has settled. I used to think that they were kind of optional until a plug-fouling problem was cured by a carb-sync...

Already done last night with my new Morgan Carbtune - great little instrument, easy to use & bullet-proof.

BTW - I plan on posting a pic of the ID of the "offending" needle-jet, to show the corrosion/cavitation that caused the problem. Good lesson to be learned here (don't let me near your carbs).

mike

[salty_monk]

Interesting... as they're brass I never thought it possible they could corrode & cause a problem like that!

Glad you fixed it

[tfb]

Good lesson to be learned here (don't let me near your carbs).

Rather the opposite: you've got so much carb-fiddling experience that you may well become the next carbie guru.

Interesting... as they're brass I never thought it possible they could corrode & cause a problem like that!

Yes, it's surprising when you come across it for the first time. I had a plug-fouling problem on my Kat1100, turned out that one of the jet needles was pitted and corroded all down one side. Why would one needle corrode but not the others, hmm? One of life's little mysteries.

[Suzuki mad]

Had the same problem with a GS1000E with CV carbs. All the idnicators were towards a blocked jet inside the carbs which were cleaned twice and heading for a third strip down.

Tunred out to be the plug cap on that cylinder was breaking down.

Suzuki mad

[hikermikem]

...turned out that one of the jet needles was pitted and corroded all down one side. Why would one needle corrode but not the others, hmm? One of life's little mysteries.

I would guess that one jet needle was made from a different material, or in a different material condition, or anodized differently perhaps??

My jet needles appear to be anodized aluminum - who knows if they are all the same??

BTW - I will never be a carb guru, but I'm sure learning a bunch-o-stuff tearing them apart!!

mike

[hikermikem]

Pics of bad needle jet

As promised, here's a pic showing the ID corrosion/cavitation on a "cut-open" naughty needle jet. This thing caused me LOTS of anguish...

[hikermikem]

Pics of bad needle jet

Another pic showing close-up corosion adjacent to a cross hole - fuel was just seeping around the jet needle...